Industrial fuels are used as combustibles for producing calories, specially in the form of hot water steam. In the maritime field these fuels are particularly useful as motor fuels in the engines of navel vessels.
These fuels are obtained by mixing fractions of heavy and light hydrocarbons. To meet the specifications of the user, the characteristics of the final product such as its viscosity, density and sulfur content are adjusted by varying the proportions of the constituents of the fuels.
As fraction of heavy hydrocarbons there are used the residues of atmospheric or vacuum distillation and/or residues of atmospheric or vacuum distallation of charges which have undergone a thermal treatment such as viscoreduction.
The light fractions called fluxants can be selected among products of direct distillation of petroleum: kerosene, illuminating oil, light gasoil, medium gasoil, heavy gasoil, products of vacuum distillation of the atmospheric residue: light gasoil under vacuum, medium gasoil under vacuum, heavy gasoil under vacuum, distillate, products of atmospheric or vacuum distillation of the effluents of the conversion units: gasoil of viscoreduction, distillate of viscoreduction, gasoil of catalytic cracker (LCO), or heavy gasoils of catalytic cracker (HCO, light oil, slurry).
This list of the different constituents of industrial fuels is not exhaustive, but mentions only the products most frequently found in the refining operation. Other less common units could likewise produce fractions that take part in the production of industrial fuels (for example, deasphalters and coke burners).
The industrial fuels resulting from these mixtures contain 3 groups of products:
(a) asphaltenes which are the heaviest molecules contained in raw petroleum, PA1 (b) resins which are polar molecules serving as "solubilization" agents of asphaltenes in the hydrocarbonated matrix, and PA1 (c) oil or matrix which is the major portion of the fuel. PA1 warping of the suction strainers, PA1 plugging of the filters, PA1 very considerable losses of charge in the transportation lines, PA1 warping of the pulverization holes, PA1 formation of deposits in the storage tanks, or PA1 coking of heating systems. PA1 saturated or unsaturated aliphatic acids having a straight or branched chain such as the fatty acids of C.sub.16 to C.sub.22, PA1 cyclic acids such as naphthenic acids, PA1 terpenic acids such as resinic acids, PA1 aromatic acids such as carboxylic alkylaryl acids.
According to the chemical nature of the matrix (aromatic, naphthenic, paraffinic), the "solubility" of the asphaltenes can be very different. It is possible to observe in certain cases a very quick dissociation of the fuel with precipitation of the heaviest molecules. This phenomenon is further accentuated in the mixture of two fuels of very different origins, that is, resulting from different crude oils. For instance, the mixture of a high asphaltenic fuel with a high paraffinic fuel (or fluxant). This phenomenon of incompatibility involves the precipitation of part of the industrial fuel.
Another source of difficulties is associated with the utilization of hydrocarbon fractions that have undergone a thermal cracking. In fact, in the last few years and in most countries of the world, the refining industry has had to adapt in order to meet an increasing demand for white product (gasoline, kerosene, motor gasoil, domestic fuel) and a decreasing demand for black products (industrial fuels). The use of conversion units that allow the production of light fractions from heavier products makes it possible to satisfy the demand of the market, but leads the refiner to use cracked products in the formula of industrial fuels (viscoreduced products, effluents of the catalytic cracker or effluents of the coke burner). These products in which the chemical structure has been deeply modified can lead to the formulation of unstable industrial fuels that change in the course of their storage and result in a progressive increase of the viscosity due to the chemical rearrangement of the reactive molecules contained in the fuel and to a precipitation of the heavier fractions as result of the flocculation of the asphaltenes.
These phenomena of precipitation of asphaltenes and increase in viscosity create difficulties both for land and maritime uses.
For land use, the exploiter can find problems such as:
In the maritime field the problems found are of the same nature, but the difficulties for exploitation become more serious for the following reasons:
The combustible contained in the ballasts is permanently shaken by the movements of the vessel (putting back in suspension the deposits formed in the ballasts). Moreover, the combustible is purified by centrifugation in the presence of water and for this reason subjected to a centrifugal force from 100 to 10,000 times greater than the terrestial attraction, and the porosity of the filters used is often less than found in land installations.
The refiner and the user have available only a few effective mens to cope with these difficulties. They can either make the formula of the fuel without incorporating cracked products, which leads the refiner to operate less efficiently and causes unbearable financial losses, or use additives. However, the existing additives, which are dispersing agents, simply delay the phenomenon of flocculation of the asphaltenes in fuels for land use which are simply subjected to land problems but prove themselves ineffective when the fuel is centrifuged in a maritime use.
The object of this invention, therefore, is to provide a composition that remains homogeneous and stable when used on land as well as when used in the maritime field.